Novel planar meglev positioning system

ABSTRACT

A novel planar meglev positioning system of the present invention mainly comprises: a platform, which has three hanging arms at the edge, and each hanging arm has a permanent magnet at the end; three impelling sets which set outside of the permanent magnet located at the end of each hanging arm, and there are impelling coils setting on each impelling set; three maglev sets, which are set corresponding each hanging arms, and there are maglev coils and permanent magnets setting on each maglev set. Due to the maglev force from the maglev coils which input controlling current, and impelling force from the impelling coils which input controlling currents, it could control the platform that enables to do 6 DOF position moving and achieve the large moving range and the motion of 6DOF with high accuracy positioning.

FIELD OF THE INVENTION

The present invention relates to a planar positioning system, and moreparticularly to an improved structure of a planar positioning systemhaving maglev positioning system thereon.

BACKGROUND OF THE INVENTION

In recent years, precision machining technologies and precision servocontrol technologies play vast important rules with the rapid growth ofthe computer information and electrics industries. Traditionally, DC orAC servo motors operated with screws are applied in most precisionpositioning systems to achieve the purpose of precision positioning. Forexample, by using piezoelectric actuator at 10 micrometer motiondistance which can reach high precision of 10 nanometers (nm), and thepiezoelectric actuator can also meet a rapid reacting request. However,the superior limit of piezoelectric actuator is the moving range. It cannot be used if there needs a larger moving range condition. In order tomeet the long distant request, most of them utilize server motor withscrew bar or directly utilize linear motors in tradition. Nonetheless,it renders the whole positioning precision down because of backlash ofscrew bar and friction of bearings. Linear motors also influenced by theripple and end effect which reduce the positioning precision.

In general, a method to solve said friction is not only strengtheningthe manufacture precision of the system hardware, but also lubricatingoil which can reduce the friction. Furthermore, it utilizes many kind ofways to estimate the friction under controlling principle and utilizesreverse force to against the friction effect.

In millimicron semiconductor fabricating process, it has reached certainlevel of technology level. At 0.9 μm fabricating process, its surfaceexamining technology will play an important role. Although it can usethe method of reducing friction method which has mentioned above to theexamining, but it would render the examining results imprecise due tothe electrostatic or shift accuracy down by few friction. It's obviousthat none-contacting force is a better way to solve the system problemabove. Aerodynamic suspension system, electrostatic suspension systemand maglev system are common examples which use none-contacting force.However, the first two are not suitable in some particular environment,e.g. clean room, vacuum room, etc. Therefore, in order to develop apositioning system with high accuracy and be able to use in manyenvironments, a system which utilizes maglev theorem to be basicconstruction has been developed. Beyond the mature technologies ofdouble axles maglev technology recently, Dr. Trumper, from MIT. USA, haspublished 6 DOF maglev positioning system which utilizes linear motorsas basic construction that also provides vertical maglev and lateralimpellent that the system needs at 1996. However, it is not easy toapply to relate industries for its complexity and difficulty.

Moreover, Dr. Trumper's student Kim, at Texas University, has designed anew 6 DOF micro-actuator which is still under developing. The systemutilizes coils and permanent magnets to achieve 6 DOF motion. Althoughit is a high precision system, but it does not suit in large movementapplication for its hardware design. Kwang and Yoon, from Korea, havedeveloped a construction that utilizes switching two dimensionalelectromagnet arrays and regulating current for rendering the platformmoving on a plane. However, it still could not surmount the boundaryproblem between coils. On the other hand, it also means that it couldnot reach the large movement request.

Moreover, according to the disadvantage of the used maglev positioningsystems, the inventor has invented a new planer maglev positioningsystem which could achieve large moving range and high 6 DOF movingaccuracy.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a novel planarmeglev positioning system that has large moving range and the motion of6 direction of field (DOF) with high accuracy positioning.

To achieve the above object, the novel planar meglev positioning systemof the present invention mainly comprises: a platform, which has threehanging arms at the edge, and each hanging arm has a permanent magnet atthe end; three impelling sets which set outside of the permanent magnetlocated at the end of each hanging arm, and there are impelling coilssetting on each impelling set; three maglev sets, which are setcorresponding each hanging arms, and there are maglev coils andpermanent magnets setting on each maglev set. Due to the maglev forcefrom the maglev coils which input controlling current, and impellingforce from the impelling coils which input controlling currents, itcould control the platform that enables to do 6 DOF position moving andachieve the large moving range and the motion of 6DOF with high accuracypositioning.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present inventionto achieve the above and other objects can be best understood byreferring to the following detailed description of the preferredembodiments and the accompanying drawings, wherein

FIG. 1 is a magnetic field vector pattern which object generates in thespace;

FIG. 2 is a magnetic field vector pattern which cylinder electromagnetgenerates in the space;

FIG. 3 is a permanent magnet forced pattern in magnetic field space;

FIG. 4(a) is an aspect of a rectangle-shaped electromagnet.

FIG. 4(b) is the forced curve between a rectangle-shaped magnet and arectangle-shaped electromagnet.

FIG. 5(a) is an aspect of a circular-shaped electromagnet.

FIG. 5(b) is the forced curve between a cylinder-shaped magnet and acylinder-shaped electromagnet.

FIG. 6 that is the structure of the invention.

FIG. 7(a) is the overlook of the platform under force of the invention.

FIG. 7(b) is the front-look of the platform under force of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIG. 1 that is a magnetic field vector pattern whichobject generates in the space, and please refer to FIG. 2 that is amagnetic field vector pattern which cylinder electromagnet generates inthe space, as shown:

According to Biot-Savart Law, the magnetic field vector which isgenerated in the space after connecting with current source is shown as:$\begin{matrix}{\overset{\rightharpoonup}{H} = {\frac{1}{4\pi}{\int_{v^{\prime}}{\frac{{\overset{\rightharpoonup}{J}\left( \overset{\rightharpoonup}{r^{\prime}} \right)} \times {\overset{\rightharpoonup}{i_{r^{\prime}}}}_{r}}{{{r^{\prime} - r}}^{2}}{\mathbb{d}v^{\prime}}}}}} & (1)\end{matrix}$

Wherein

is a view point position vectors

is a surface current position vector

(

¹) is the current density of the coil

_(r),_(r) is a vector opposite of the view point and surface current. Byapplying the equation on the cylinder and rectangle electromagnets, wehave got magnetic field vector in space as following equation:$\begin{matrix}{{\overset{\rightharpoonup}{H}}_{cyl} = {\frac{1}{4\pi}{\int_{- h_{1/2}}^{h_{1/2}}{\int_{0}^{2\quad\pi}{\int_{r_{1}}^{r_{2}}{\left( \frac{{NI}_{cyl}}{\left( {r_{2} - r_{1}} \right)h_{1}} \right)\frac{\left( {{\overset{\rightharpoonup}{e}}_{\phi^{\prime}} \times {\overset{\rightharpoonup}{e}}_{p^{\prime}p}} \right)}{{{\overset{V}{p} - {\overset{V}{p}}^{\prime}}}^{2}}r^{\prime}{\mathbb{d}r^{\prime}}{\mathbb{d}\phi^{\prime}}{\mathbb{d}z^{\prime}}}}}}}} & (2)\end{matrix}$

Wherein h₁ is coil's height N is coil's winding turns r₁ and r₂represent internal and external diameter of the coils I_(cyl) is aninput current of the coil

_(cyl) is product of position function and current in space.

We rewrite the equation as following: $\begin{matrix}{{\overset{\rightharpoonup}{H}}_{cyl} = {{{\overset{\rightharpoonup}{h}}_{cyl}\left( {x,y,z} \right)}I_{cyl}}} & (3)\end{matrix}$

With the same reason, we got the magnetic field that rectangularelectromagnet generates is: $\begin{matrix}{{\overset{\rightharpoonup}{H}}_{rec} = {{{\overset{\rightharpoonup}{h}}_{rec}\left( {x,y,z} \right)}I_{rec}}} & (4)\end{matrix}$please refer to FIG. 3 that is a permanent magnet forced pattern inmagnetic field space. From Lorentz force, we got a equation of apermanent magnet forced in magnetic field space: $\begin{matrix}{\overset{\rightharpoonup}{F} = {\left( {\overset{\rightharpoonup}{m} \cdot \nabla} \right)\overset{\rightharpoonup}{B}}} & (5)\end{matrix}$

Wherein

is a dipole vector of the magnet.

From equation (3) and equation (4), it is not difficult to find that themagnet force that magnet generates in electromagnet field and can beshown as: $\begin{matrix}{\overset{\rightharpoonup}{F} = {{\overset{\rightharpoonup}{g}\left( {x,y,z} \right)}I}} & (6)\end{matrix}$

Wherein

(x,y,z) is a opposite position function of the magnetic in theelectromagnet. In order to get the relating function of

(x,y,z), we avoid complicated theory or finite element method (FEM) toget the force of the magnet in the coil. We use high precision machinedevice to measure the force in the coil and rid of current value to getthe curve of

(x,y,z).

Please refer to FIG. 4(a) and FIG.4(b) that are the patterns of arectangle-shaped electromagnet and the forced curve between arectangle-shaped magnet and a rectangle-shaped electromagnet, as shown:

For rectangular magnet and rectangular electromagnet to be example, set100 measuring points inside the coil and put the magnets on them, thenget the force value of magnets in different current from those points,and utilize those measured data and multinomial curve to get:F _(rec,y)=(a ₆ y ⁶ + ₅ y ⁵ +a ₄ y ⁴ +a ₃ y ³ +a ₂ y ² +a ₁ y+a ₀)I_(rec)   (7)

Wherein a₆=−1.954×10⁹, a₅=4.39×10⁸, a₄=−3.385×10⁷, a₃=1.16×10⁶,a₂=−19338, a₁=214.8, a₀=−0.385. Therefore, we can get the relatingfunction of

(x,y,z) between rectangular magnet and rectangular Electromagnet.

Please refer to FIG. 5(a) and FIG. 5(b) that are the patterns of acircular-shaped electromagnet and the force curve between acylinder-shaped magnet and a cylinder-shaped electromagnet, as shown:

Similarly, we get the relating function of

(x,y,z) between circular magnet and cylinder electromagnet by using thesame way as above:_(cyl,z)=(b ₄ z ⁴ +b ₃ z ³ +b ₂ z ² +b ₁ z+b ₀)I _(cyl)   (8)

Wherein b₄=−5.62×10⁶, b₃=−4.89×10⁵, b₂=−16659, b₁=−219.34, b₀=0.06619.

Please refer to FIG. 6 that is the structure of the invention, as shown:

The present invention, a novel planar maglev positioning system 1,comprises: a platform 10, which has three hanging arms 101-102-103 atthe edge, and each hanging arm 101-102-103 has set a permanent magnet104-105-106 at the end; three impelling sets 11-12-13, which are set onthe relative positions of the permanent magnets 104-105-106 located ofthe end of each hanging arms 101-102-103, and there are impelling coils111-121-131 setting on each impelling sets 11-12-13 to provide impellingforce when input control current into impelling coils 111-121-131; threemaglev sets 14-15-16, which are set corresponding each hanging arms101-102-103, and there are maglev coils 141-151-161 and permanentmagnets 142-152-162 setting on each maglev set 14-15-16, to providelevitated forces when input control current into meglev coils141-151-161. Wherein the material of the platform 10 and three hangingarms 101-102-103 can be aluminum alloy, and these three hanging arms101-102-103 can be “

” shape strength structure. Besides, one of the three handing arms101-102-103 can be bent shape.

Please refer to FIG. 7(a) and FIG. 7(b) that are the overlook andfront-look patterns of the platform under force of the invention, asshown:

By Newtonian second mechanics law, we get forced equations and torqueequations of the platform from the six magnetic force of FIG. 7(a) andFIG. 7(b):ΣF _(x) =F ₁−{square root}{square root over (2)}/2F ₃ =M{umlaut over(X)}ΣF _(y) =F ₂+{square root}{square root over (2)}/2F ₃ =MŸΣF _(z) =F ₄ +F ₅ +F ₆ −Mg=M{umlaut over (Z)}ΣT _(x) =−F ₅ l ₁+{square root}{square root over (2)}/2F ₆ l _(2≅I)_(XX{umlaut over (φ)})ΣT _(y) =F ₄ l ₁−{square root}{square root over (2)}/2F ₆ l ₂ ≅I_(YY{umlaut over (φ)})ΣT _(z) =F ₃ L ₃ ≅I _(ZZ{umlaut over (θ)})  (9)

Wherein M is mass of the platform, g is acceleration of gravity,I_(XX)-I_(YY) and I_(ZZ) are rotating inertia of the platform along X-Yand Z axles. Go back to equation (7) and (8), we can rewrite the abovematrix into:{overscore (M)}{umlaut over (W)}=B(W)U−G   (10)

Wherein {overscore (M)}≡diag[M, M, M, I_(XX), I_(YY), I_(ZZ)], X≡[X, Y,Z, φ, φ, θ]^(T), U≡[u₁u₂, u₃, u₄, u₅, u₆]^(T), G≡[0, 0, Mg, 0, 0,0]^(T).

From the equations above, utilizing impelling force F₁-F₂-F₃ when inputcontrol current into impelling coil 111-121-131 can precisely controlthe platform 10 moving along X-Y axle, and rotating along Z axle (θ),and utilizing meglev coils 141-151-161 to input control current togenerate levitated forces F₄-F₅-F₆ can precisely control the platform 10moving along Z axle and rotating along X, Y axle (φ, φ). Thus, itachieves large moving range and the motion of 6 DOF with high accuracypositioning.

1. A novel planar meglev positioning system, comprising a platform,which has three hanging arms at the edge, and each hanging arm has apermanent magnet at the end; three impelling sets which are set on therelative positions of the permanent magnets located at the end of eachhanging arm, and there are impelling coils setting on each impellingset; three maglev sets, which are set corresponding each hanging arms,and there are maglev coils and permanent magnets setting on each maglevset.
 2. A novel planar meglev positioning system as claimed in claim 1,wherein the material of the said platform and said three hanging armscan be aluminum alloy
 3. A novel planar meglev positioning system asclaimed in claim 1, wherein said three hanging arms can be “

” shape
 4. A novel planar meglev positioning system as claimed in claim1, wherein one of said three handing arms can be bent shape.